1. Field of Invention
The present invention relates to cassettes for holding and dispensing a plurality of microscope slides, such as are used for blood smear specimens, and more particularly to improved constructional features of such cassettes and of a cooperative slide ejection assembly of apparatus for automatically producing blood smear slides.
2. Background Art
The above-noted U.S. application Ser. No. 08/557,226, describes apparatus for automatically producing a plurality of blood smear specimens respectively upon a succession of glass microscope slide elements supplied to the apparatus. In order to operate in a reliable fashion, this apparatus requires a system for reliably providing a plurality of slides seriatim into a predetermined ingress orientation for precise pick up and handling by the operative stations of the automated slidemaker. Such slides are marketed in a plurality of different packages. To assure proper slide supply, it is desirable to have a cassette that is conveniently loadable with a large number, e.g. 100, of slides from those packages, and that will safely store those slides during handling and insertion into the slidemaker apparatus. The cassette also should interfit and cooperate with the automated slidemaker in: (i) assuring reliable, single-slide ejections to provide an unbroken succession of slides and (ii) signaling the apparatus promptly upon the cassette becoming empty.
U.S. Pat. No. 5,209,903 describes one cassette construction that is intended to achieve safe slide storage, reliable feed and empty detection capabilities. This cassette has a bottom outlet passage for slide feed; and, in order to prevent slides from falling out of this passage, provides a cassette shutter member that must be opened by the slidemaker apparatus. However, the slide stack remains loose within the cassette, necessitating careful handling of the cassette. The '903 patent system utilizes special slides, having a frosted area for data printing, and a photodetector on the slide ejection mechanism senses such frosted area to determine a cassette-empty condition. While the cassette and slide ejection system of the '903 patent appears quite functional, it would be desirable to have a system which retains and controls a slide stack more effectively and which does not require special slide characteristics to signal a cassette-empty condition.